[llvm] [coroutines] Use DILocation from new storage for hoisted dbg.declare (PR #75104)

[Wei Wang via llvm-commits]

https://github.com/apolloww created https://github.com/llvm/llvm-project/pull/75104

After hoisting, the dbg.declare is moved into the block that defines the new storage. This could create an inconsistency in the debug location scope hierarchy where the scope of hoisted dbg.declare (i.e. DILexicalBlock) is enclosed with the scope of the block (i.e. DISubprogram). This confuses LiveDebugValues pass to think that the hoisted dbg.declare is killed in that block and does not generate DBG_VALUE.

>From ce003bf24cb18a7074c7308b75bbfd8c71005842 Mon Sep 17 00:00:00 2001
From: Wei Wang <apollo.mobility at gmail.com>
Date: Thu, 16 Nov 2023 13:40:41 -0800
Subject: [PATCH] [coroutines] Use DILocation from storage for hoisted
 dbg.declare

---
 llvm/lib/Transforms/Coroutines/CoroFrame.cpp  |  6 ++--
 .../Coroutines/coro-debug-frame-variable.ll   | 29 ++++++++++---------
 2 files changed, 20 insertions(+), 15 deletions(-)

diff --git a/llvm/lib/Transforms/Coroutines/CoroFrame.cpp b/llvm/lib/Transforms/Coroutines/CoroFrame.cpp
index 1134b20880f183..2c43f49e712f20 100644
--- a/llvm/lib/Transforms/Coroutines/CoroFrame.cpp
+++ b/llvm/lib/Transforms/Coroutines/CoroFrame.cpp
@@ -2887,9 +2887,11 @@ void coro::salvageDebugInfo(
   // dbg.declare does.
   if (isa<DbgDeclareInst>(DVI)) {
     std::optional<BasicBlock::iterator> InsertPt;
-    if (auto *I = dyn_cast<Instruction>(Storage))
+    if (auto *I = dyn_cast<Instruction>(Storage)) {
       InsertPt = I->getInsertionPointAfterDef();
-    else if (isa<Argument>(Storage))
+      if (I->getDebugLoc())
+        DVI->setDebugLoc(I->getDebugLoc());
+    } else if (isa<Argument>(Storage))
       InsertPt = F->getEntryBlock().begin();
     if (InsertPt)
       DVI->moveBefore(*(*InsertPt)->getParent(), *InsertPt);
diff --git a/llvm/test/Transforms/Coroutines/coro-debug-frame-variable.ll b/llvm/test/Transforms/Coroutines/coro-debug-frame-variable.ll
index 37b4126ce37304..53995fb3498e59 100644
--- a/llvm/test/Transforms/Coroutines/coro-debug-frame-variable.ll
+++ b/llvm/test/Transforms/Coroutines/coro-debug-frame-variable.ll
@@ -31,8 +31,8 @@
 ; CHECK:       entry:
 ; CHECK:         %j = alloca i32, align 4
 ; CHECK:         call void @llvm.dbg.declare(metadata ptr %j, metadata ![[JVAR:[0-9]+]], metadata !DIExpression()), !dbg ![[JDBGLOC:[0-9]+]]
-; CHECK:         %[[MEMORY:.*]] = call ptr @new
-; CHECK:         call void @llvm.dbg.declare(metadata ptr %[[MEMORY]], metadata ![[XVAR:[0-9]+]], metadata !DIExpression(DW_OP_plus_uconst, 32)), !dbg ![[IDBGLOC:[0-9]+]]
+; CHECK:         %[[MEMORY:.*]] = call ptr @new({{.+}}), !dbg ![[IDBGLOC:[0-9]+]]
+; CHECK:         call void @llvm.dbg.declare(metadata ptr %[[MEMORY]], metadata ![[XVAR:[0-9]+]], metadata !DIExpression(DW_OP_plus_uconst, 32)), !dbg ![[IDBGLOC]]
 ; CHECK:         call void @llvm.dbg.declare(metadata ptr %[[MEMORY]], metadata ![[IVAR:[0-9]+]], metadata !DIExpression(DW_OP_plus_uconst, 20)), !dbg ![[IDBGLOC]]
 ; CHECK:       await.ready:
 ;
@@ -48,18 +48,20 @@
 ; CHECK:       await.ready:
 ;
 ; CHECK-DAG: ![[IVAR]] = !DILocalVariable(name: "i"
-; CHECK-DAG: ![[SCOPE:[0-9]+]] = distinct !DILexicalBlock(scope: !6, file: !1, line: 23, column: 12)
-; CHECK-DAG: ![[IDBGLOC]] = !DILocation(line: 24, column: 7, scope: ![[SCOPE]])
+; CHECK-DAG: ![[PROG_SCOPE:[0-9]+]] = distinct !DISubprogram(name: "foo", linkageName: "_Z3foov"
+; CHECK-DAG: ![[BLK_SCOPE:[0-9]+]] = distinct !DILexicalBlock(scope: ![[PROG_SCOPE]], file: !1, line: 23, column: 12)
+; CHECK-DAG: ![[IDBGLOC]] = !DILocation(line: 23, column: 6, scope: ![[PROG_SCOPE]])
 ; CHECK-DAG: ![[XVAR]] = !DILocalVariable(name: "x"
 ; CHECK-DAG: ![[JVAR]] = !DILocalVariable(name: "j"
-; CHECK-DAG: ![[JDBGLOC]] = !DILocation(line: 32, column: 7, scope: ![[SCOPE]])
+; CHECK-DAG: ![[JDBGLOC]] = !DILocation(line: 32, column: 7, scope: ![[BLK_SCOPE]])
 
 ; CHECK-DAG: ![[XVAR_RESUME]] = !DILocalVariable(name: "x"
-; CHECK-DAG: ![[IDBGLOC_RESUME]] = !DILocation(line: 24, column: 7, scope: ![[RESUME_SCOPE:[0-9]+]])
-; CHECK-DAG: ![[RESUME_SCOPE]] = distinct !DILexicalBlock(scope: !22, file: !1, line: 23, column: 12)
+; CHECK-DAG: ![[RESUME_PROG_SCOPE:[0-9]+]] = distinct !DISubprogram(name: "foo", linkageName: "_Z3foov"
+; CHECK-DAG: ![[IDBGLOC_RESUME]] = !DILocation(line: 24, column: 7, scope: ![[RESUME_BLK_SCOPE:[0-9]+]])
+; CHECK-DAG: ![[RESUME_BLK_SCOPE]] = distinct !DILexicalBlock(scope: ![[RESUME_PROG_SCOPE]], file: !1, line: 23, column: 12)
 ; CHECK-DAG: ![[IVAR_RESUME]] = !DILocalVariable(name: "i"
 ; CHECK-DAG: ![[JVAR_RESUME]] = !DILocalVariable(name: "j"
-; CHECK-DAG: ![[JDBGLOC_RESUME]] = !DILocation(line: 32, column: 7, scope: ![[RESUME_SCOPE]])
+; CHECK-DAG: ![[JDBGLOC_RESUME]] = !DILocation(line: 32, column: 7, scope: ![[RESUME_BLK_SCOPE]])
 define void @f() presplitcoroutine !dbg !8 {
 entry:
   %__promise = alloca i8, align 8
@@ -71,13 +73,13 @@ entry:
   br i1 %alloc, label %coro.alloc, label %coro.init
 
 coro.alloc:                                       ; preds = %entry
-  %size = call i64 @llvm.coro.size.i64()
-  %memory = call ptr @new(i64 %size)
-  br label %coro.init
+  %size = call i64 @llvm.coro.size.i64(), !dbg !23
+  %memory = call ptr @new(i64 %size), !dbg !23
+  br label %coro.init, !dbg !23
 
 coro.init:                                        ; preds = %coro.alloc, %entry
-  %phi.entry.alloc = phi ptr [ null, %entry ], [ %memory, %coro.alloc ]
-  %begin = call ptr @llvm.coro.begin(token %id, ptr %phi.entry.alloc)
+  %phi.entry.alloc = phi ptr [ null, %entry ], [ %memory, %coro.alloc ], !dbg !23
+  %begin = call ptr @llvm.coro.begin(token %id, ptr %phi.entry.alloc), !dbg !23
   %ready = call i1 @await_ready()
   br i1 %ready, label %init.ready, label %init.suspend
 
@@ -239,3 +241,4 @@ declare void @llvm.memset.p0.i64(ptr nocapture writeonly, i8, i64, i1 immarg)
 !20 = !DILocation(line: 43, column: 3, scope: !7)
 !21 = !DILocation(line: 43, column: 8, scope: !7)
 !22 = distinct !DILexicalBlock(scope: !8, file: !1, line: 23, column: 12)
+!23 = !DILocation(line: 23, column: 6, scope: !8)